DAVID L. MILLS (1938-2024)

BY VINT CERF AND STEVE CRANG

DAVID LENNOX MILLS — professor emeritus of electrical and computer engineering and of computer and information sciences at the University of Delaware, and an Internet pioneer who built the first version of the National Science Foundation Network (NSFNET) and solved a crucial challenge to synchronize networked devices — died on Jan. 17, 2024, at the age of 85.

David was born in Oakland, California, on June 3, 1938. His mother, Adele (née Dougherty), was a pianist, and his father, Alfred, was an engineer. He was born with glaucoma, but a surgeon saved some of the vision in his left eye when he was a child. He attended a school for the visually impaired in San Mateo, California. A teacher’s comment that, because of his disability, he would never go to college further inspired the headstrong young David to do just the opposite. It was “like waving a flag in front of a bull,” he later told a journalist.

After graduating from high school, David went on to complete his undergraduate and graduate studies at the University of Michigan, earning bachelor’s degrees in engineering science (1961) and mathematics (1961), as well as master’s degrees in electrical engineering (1962) and communication sciences (1964), before completing his Ph.D. in computer and communications science (1971). In 1964, he met his future wife, Beverly Csizmadia; both were students at the University of Michigan. They married in 1965. Their daughter, Eileen, was born in 1965, and their son, Keith, followed in 1968.

During his graduate studies, David performed early research into distributed computing and worked on the ARPA-sponsored Conversational Use of Computers project, which developed hardware and software for a Digital Equipment Corporation (DEC) PDP-8 minicomputer that allowed terminals such as teletypes to connect over phone lines to an IBM 360/67 mainframe. His data concentrator was almost certainly the first non-IBM device to be connected to an IBM channel.

After completing his Ph.D. study at Michigan, David worked at the University of Edinburgh (1971-72), the University of Maryland (1972-77), COMSAT Corporation (1977-82), and Linkabit Corporation (1982-86) before joining the faculty of the University of Delaware in 1986. He became an emeritus faculty member at Delaware in 2008.

While at Maryland, David invented “The Fuzzball,” the first modern router and application server; it was used for network prototyping. Fuzzballs were DEC PDP-11 computers loaded with David’s software. Six Fuzzball routers were later used in 1986 to build the first 56 kb/sec backbone of NSFNET, which evolved into the modern Internet, and this deployment allowed for the further development and testing of the TCP/IP protocols.

After departing Maryland he worked for the COMSAT Corporation, where his work brought him into close contact with researchers working on the ARPANET, a precursor to the Internet. David began his work on the Network Time Protocol (NTP), a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks, and in doing so addressed the many challenges related to maintaining time in the face of devices and network branches operating with differing speeds and latencies.

NTP was first implemented in 1985 and tested on the Fuzzball-driven NSFNET. By 1988, David had refined NTP to the point where it could synchronize the clocks of connected computers that had been telling significantly differing times to within tens of milliseconds, and later to within a few microseconds.

During this time, David served as the first chair of the Internet Engineering Task Force, a standards organization for establishing Internet standards, and actively participated in the evolution of IP, TCP, TELNET, FTP, SMTP, and related protocols that are now widely used in the Internet.

The current version of NTP, Version 4, was released in 2010 and continues to keep time for all manner of Internet-connected devices, ensuring that all kinds of computers and other Internet-connected devices worldwide, from mobile phones to air traffic control centers, run “on time” and ensuring that our interconnected world runs smoothly.

David’s most important publications on his work include “The Fuzzball,” published in 1988 in the Computer Communication Review, a magazine of the Association for Computing Machinery’s SIGCOMM, and “Internet Time Synchronization: The Network Time Protocol,” published in the IEEE Transactions on Communications in October 1991, which described the protocol and how its architecture and algorithms maintained distributed timekeeping, even in cases of failures and disruption. He followed these with Network Time Synchronization: The Network Time Protocol on Earth and in Space (CRC Press, 2nd ed., 2010), a textbook last updated in 2011 that describes the principles of time synchronization, how NTP works, and the development of the protocol over time.

David was elected to the U.S. National Academy of Engineering in 2008. He was also a member of the Internet Society, the American Association for the Advancement of Science, and was a fellow of both the Association for Computing Machinery and the Institute of Electrical and Electronics Engineers (IEEE). He was recognized in 2013 with the IEEE Internet Award “for significant leadership and sustained contributions in the research, development, standardization, and deployment of quality time synchronization capabilities for the Internet.”

While at the University of Delaware, David and his wife Beverly, a Delaware alumnae, funded the David L. and Beverly J.C. Mills Chair of Computer and Information Sciences. The position rewards exceptional young female faculty talent in the Departments of Electrical and Computer Engineering or Computer and Information Sciences.

Outside of his career’s many achievements, David’s hobbies included running an amateur radio station (W3HCF) out of his home in Newark, Delaware. He was also a member of the American Radio Relay League, the Radio Society of Great Britain, and the Amateur Satellite Organization.

David is survived by his wife Beverly Mills, his daughter Eileen Schnitzler, his son Keith Mills, and his brother Gregory Mills.